B9. 4 Circulatory System

Question 1

how does the circulatory system work in unicellular organisms

Answer 1

In unicellular organisms, exchange of materials occurs easily by simple diffusion through the cell surface membrane.

Question 2

how do multicellular organs not respire

Answer 2

In multicellular organisms, diffusion is inadequate for transport.

Question 3

why does diffusion not work in multicellular organs for respiration

Answer 3

o larger body, reduced surface area to volume ratio

o numerous cells situated deep in the body, far from external environment

Question 4

what is blood made up of

Answer 4

Blood is made up of plasma, red blood cells, white blood cells and platelets.

Question 5

what do red blood cells do

Answer 5

• Red blood cells carry oxygen (to be transported to all cells of the body).

Question 6

what do white blood cells do

Answer 6

• White blood cells are involved in antibody production and phagocytosis.

Question 7

what do platelets do

Answer 7

• Platelets are involved in blood clotting.

Question 8

what does plasma do

Answer 8

Plasma is involved both in the transport of blood components and other dissolved substances including hormones, antibodies, urea and carbon dioxide, and in the distribution of heat.

Question 9

what other substances other than blood does plasma transport

Answer 9

hormones, antibodies, urea and carbon dioxide, and in the distribution of heat.

Question 10

how does oxygen go from breathing into blood

Answer 10

As blood passes through the lungs, oxygen diffuses from alveoli (air sacs) into the blood.

Question 11

what happens when haemoglobin reacts with oxygen

Answer 11

combines reversibly with oxygen to form oxyhaemoglobin

Question 12

what does haemoglobin do

Answer 12

• Haemoglobin combines reversibly with oxygen to form oxyhaemoglobin.
• Red blood cells transport oxyhaemoglobin to all tissues of the body. As blood passes through tissues, oxyhaemoglobin releases oxygen, which diffuses in solution into tissue cells.

Question 13

what is oxyhaemoglobin able to do

Answer 13

• Red blood cells transport oxyhaemoglobin to all tissues of the body. As blood passes through tissues, oxyhaemoglobin releases oxygen, which diffuses in solution into tissue cells.

Question 14

what transports oxyhaemoglobin

Answer 14

• Red blood cells transport oxyhaemoglobin to all tissues of the body. As blood passes through tissues, oxyhaemoglobin releases oxygen, which diffuses in solution into tissue cells.

Question 15

describe the double circulatory system

Answer 15

Blood passes through the heart twice in one complete circuit as it moves from the pulmonary circulation and into the systemic circulation.

Question 16

what is pulmonary circulation

Answer 16

Pulmonary circulation: linking the lungs to the heart

Question 17

what is systemic circulation

Answer 17

Systemic circulation: around the body

Question 18

what are the advantages of a double circulatory system

Answer 18

Blood enters the lungs at a lower pressure than blood leaving the heart > ensures that blood flows slowly through the lungs, allowing sufficient time for it to be fully oxygenated.

Heart pumps oxygenated blood at high pressure to the rest of the body, ensuring oxygenated blood is distributed to tissues quickly > helps maintain high metabolism

Question 19

how does heart pumping blood at high pressure affect the body

Answer 19

ensuring oxygenated blood is distributed to tissues quickly > helps maintain high metabolism

Question 20

describe the passage of blood through the heart

Answer 20

superior + inferior vena cava
right atrium
tricuspid valve
right ventricle
semilunar valve
pulmonary artery (pulmonary arch)
lungs
pulmonary veins 
left atrium
bicuspid valve
left ventricle
semilunar valve
aorta

Question 21

what does the superior vena cava collect blood from

Answer 21

blood from head, neck and arms returned by superior (anterior) vena cava

Question 22

what does the inferior vena cava collect blood from

Answer 22

blood from other parts of body (except lungs) returned by inferior (posterior) vena cava

Question 23

once oxygenated blood reaches the aorta, how is blood distributed

Answer 23

From aorta, blood is distributed to all parts of the body (except the lungs).

Question 24

name the 7 steps that describe the passage of blood through the circulatory system

Answer 24

1. Deoxygenated blood from various parts of the body is returned to the right atrium.
2. Right atrium contracts, blood flows into right ventricle.
3. Right ventricle contracts, blood leaves the heart through pulmonary arch and enters the lungs via pulmonary arteries.
4. Oxygenated blood from the lungs is brought back to left atrium by pulmonary veins.
5. Left atrium contracts, blood flows into left ventricle.
6. Left ventricle contracts, blood leaves through aorta.
7. From aorta, blood is distributed to all parts of the body(except the lungs).

Question 25

how do ventricles and atria contract

Answer 25

*Atria and ventricles contract alternately.